Rubber composition and method of preserving rubber



Patented May 7, 1935 ffUNiTEo Sma COMPOSITION AND METHOD OF rnnsnavnvqnnnnnn Q RUBBER PATENT OFFICE '20 Claims. I or. 18- 50)' This invention relates to the art of preserving rubber, eitheriin the vulcanized or unvulcanized condition, and to rubber compositions so .pre-

served. V

It iszwell knownthatrubber gradually loses its strength and resiliency, particularly when exposed tolight, heat, and air, such deterioration being commonly attributed to an oxidation of the rubber or the rubbercomposition. Various substances, known generally as age-resisters or anti-oxidants, have-been added to rubber for the purpose of re- ;tarding its deterioration. Amongthe most successful of. thesefsubstances are the secondary aromatic amines and the condensation products of aldehydes with primary aromatic amines. This invention, in brief, consists in'treatingrubber with a member of a new class of age-resisters, namely, condensation products of ketones with primary aromatic amines. Such substances in general have age-resisting properties, but'the best *result'swere secured by using the condensation products of amines withaliphatic ketones. It was also found that substituted or condensed ring amines produced more active products than the .-simpler amines. Thus, p-toluidine produces con siderably better condensation products than aniline, andalpha-naphthylamine still better However, any. primary aromatic amine, such as aniline,

the toluidines, the xylidines, anisidine, phenete- -dine, p-phenylene-diamine, alpha andabeta naph "thylamine, the naphthylene diamines, mono or v diamino-diphenylamine, etc., may be condensed H with ketones such as acetophenone, benzophenone,

. benzoyl acetone, cinnamone, hydroxy benzal acetone, dibenzal acetone, benzoin, etc., but preferably with aliphatic ketones such as acetone, cyclo- .hexanone, acetyl acetone, mesityl oxide, phorone, 7

diacetone. alcohol, hydroxy acetone, hydracetyl acetone, etc. The unsaturated or hydroxy-substituted aliphatic ketones appear to give particu- ,larly good condensation products-with primary 'aromatic amines. Any one of. the above-mentioned class of ketone-amine condensation products may be incorporated into rubber. or a rubber composition with beneficial efiects on its age-resisting. properties, preferably from 0.2 to 5 parts by condensation "product of cyclohexanone and.

results:

alpha-naphthylamine was prepared by mixing ;30 parts by weight of cyclohexanone and 45 parts of The excess of .unreacted materials was finallyremoved byvdistilling' up to a temperature of 340 F.

alpha-naphthylamine.f The, mixture was heated under a reflux condenser for 8 hours, during which time the materials reacted and split out water.

A typical tire tread composition was prepared containing blended plantation rubbers 100 parts by weight, sulfur 5.5'parts, zinc oxide 30 parts, gas

black 40 parts, mineral rubber -10parts, palm oil, 7

prepared as described above. The compositions were thorcughlymixed, and vulcanized in'a press for 45 minutes at 294 F. to produce an optimum cure. The vulcanized compositions weretested to, compare their relative rates of aging,- by measuring their tensile strength and elongation at the breaking point before and after aging. The accelerlated aging was carried out in the Geer aging oven, in which the? samples were maintained at' a tem- -perature..of"158- F. ina constantly renewed current of air. The results are shown in the table below.- 7 v .Tcnsile strength lbs; per sq. in. and elongation r at-the breaking point f Before aging lg ggg the Tensile Elonga- Tensile Elongastrength tion strength tion I Per cent 1 Per cent -Without age-resister.. 3590 667- 1633 p 495 With-age-resister- 3795 685 2702 530 Example 2. -As another specific example of the process of this invention a condensation product waspreparedby mixing 98 parts by weight of mesityl-oxide (l molecularoequivalent) and 143 parts alpha naphthylamine (I molecular equivalent) ;-.and 143 parts alpha-naphthylamine (1 molecular equivalent) with 0.2parts sulfuric acid, and heating for 8 hours under a reflux condenser.

The product was avery dark syrupy liquid. Rubber compositions were prepared similar to those given above, 1 but containing the mesityl oxidealpha-naphthylamine condensation produce as age-resister. 1 After vulcanization the compositions'were'testedas before with the following Tensile strength in lbs. per sq. in. and elongation at the breaking point Before aging I After 7 days in the Gear oven Tensile strength Tensile Elonga- Elongastrength tion Per-cud 690 ,ms; 687 2748 Without age-resistor With age-resister Example 3.-As another-{specific f xenipie ot: the process of this invention, condensation;

products were prepared of diacetone alcohol with aniline, and with alpha proximately equimolecular 'Zm' lthe" cprises treating rubber with a reaction product of one case 120 parts by weight of diaoetone' alcohol were mixed with 93 parts of aniline, and in the other case with 143 parts of alpha naphthylaimine, and the mixtures were heated to :dnive ,-ofl' the water formed by the reaction. The

,1 7' 'H ens'ile strength so products were 7 respectively dark .red and .black syrupy liquids. The products were incorporated into rubber compositions and the "vulcanized compositions tested before and after -.aging as .in Example 1 above, with-the iollowing results:

in lbs. per sqain. and elongation :at the breaking point From the examples given above it is {evident that the condensation products'rof ketones and aromatic amines are extremely effective :in.;retarding the deteriorationwhich rubbersnormalhr undergoes upon aging. Obviously the proper;- tions of the materials used in thelrubber composition may be varied to meet any individualrequirements, or rubber compositions of a widely diiferen't nature, such as'innertubetire "friction, hose cover, pure 'gum thread or other compositions may be employed, the beneficial effect of the addition of a ketone-amine condensation product being :observed in general in rubber exposed to oxidation. .These condensation ,products may also be applied to unvulcanized or vulcanized rubber with good eiiect'on the age-insisting properties of the rubber, such as by applyingthem to the surface of the rubber, as'i'orexamplein sdlu'tionyor in 'theiormof a paste -or emulsion.

"It is to be understood' that the tenn" treating as employed in the appended claims ts .aused in -a generic sense to include either the incorporation of the condensation products -'of *ketones iandaromatic amines into the rubber by milling or similar'pro'cess, or bymi-xing with the rubber latex before "coagulation, or to the application thereof to the surface of a mass-of crude or vulcanized rubber; The term rubbeflis' Iikewisecemployed in the claims in-a generic sense to include caou'tchouc, balata, gutta percha; rubber isomers and like-products, whether-or not-admixed withfillers, :pigments, vulcanizing or accelerating agents. The word ary is herein employed to refer i ior, as hitherto stated, the precise proportions of,

materials having equivalent chemical properies to univalent aromatic hydrocarbon radicals whose free valence belongs to the nucleus and not to a side chain.

While we have herein disclosed with considemble particularity certain preienrcd manners ofperfo'rm'ing our invention, we do not thereby desire or intend to limit ourselves solely thereto,

the materials utilized may be varied and other 10 maybe employed if desired without departing IIOZIi the spirit and scope of the invention as defined in the appended claims.

'Elhisfisradivisicn of our co-pending application Serial'No. 301,440, filed August 22, 1928.

'Dhe methodvof preserving rubber which coma ketonecontaining not more than two oxygen atoms with an aromatic amine containing both .primanz and secondary ammoagroups;

2. fT-hemethodof prcservingmbber which comprises treating .rubber witha reaction pm'dnct at an aliphatic ketone containing not more gtwoaoxygen atomswithzan aromatic-amine containing both primary and-secondary i3. The method of .preserv ingimbberwhichzcomprises treating rubber with a reaction acetone with an aromatic amino :contaiining'both primary and secondary nminoigronps. Themethod of preservingrubberwhichzmnprises. treating rubber with :a .reactimi product of a1 ketone containing .not "more than LtWO i atoms with a-primazry aminofdiarylamine. k

5. Themethodiof preservingirubberwvhichlcomprises I-treating rubber with a reaction -:pmduct :of an-aliphatic ketonescontaining :not more than 50 ."two oxygen atoms with :a primanyfazmmo ,diarylamme. -6. The methodaofmrescrvingrrubberwhichmmno prises treating rubber-Ninth :a. reaction moductzof acetone 'with'sa primary amino :diarylamine.

I. The method of vpreservingrubber which cum- ;prises treating :mbber with :a 'reactionnn'odnct-of a :ketone containing mot .more thani .0 oxygen -atomsvwithamino diphenylannne. 5v 8. 'Ifnezmethod of :preservzingmbber' which coniprises .tneatingrubber :2. reaction product (OI acetone with'amino diphenylamine. V l I 9., .Themethodoi preserwing-nubherwhich com- .lprises :treating rrubber wvitha iof zakketone containing mot more than'itwobxygm atomsilwithediamino :diphenylamine. Y

' .il0.-.The method oft-preserving :ubher'which conmrisesftreating rubber with azreactioniprnduc --oizaoetone=with:diamino'diphenylamima.

.rlilzflhe method of vpreserving :rubber which acompiiises vmcamizing rubber in-thepresenoe nof the reactionaproducttof acetone and amino niphe- 12. The .method :of presenting mubber, which comprises vulcanizing rrubber in ztherpresence of the reaction product of acetone :and diamin'o-' slip'henylamine. r --13. A 'rubber composition comprising subber :andw. reaction product of :aiketonecontainmgnot more than :two oxygen atoms with an aromatic amine containing both primary andisecondary amino groups.

J14. .Arubbericomposition comprising :rubberand v:a reaction product of :a :ketone \containing not :more than' atwo oxygen :atoms*with :an :amino :diarylamine. v

'15. A rubber-composition compr'ising nibber :and a reaction product or a 'ketonecomammg not more thantwo oxygen atoms with amino diphenylamine.

16. A rubber composition comprising rubber and a reaction product of a ketone containing not more than two oxygen atoms with diamino diphenylamine.

1'7. A rubber composition comprising rubber and the reaction product of acetone and amino diphenylamine.

18. A rubber composition comprising rubber and the reaction product of acetone and diamino diphenylamine.

19. A vulcanized rubber composition which has been vulcanized in the presence of a reaction product of acetone with amino diphenylamine.

20. A vulcanized rubber composition which has been vulcanized in the presence of a reaction product of acetone with diamino diphenylamine.

' WALDO L. SEMON.

ARTHUR W. snow. '7

CERTIFICATE OF CORRECTION.

Patent No. 2,000,041 May 7, 1955.

Henry Van Arsdale a Acting Commissioner of Patents. 

